Fuel cells are suitable for obtaining electrical energy from chemical energy carriers without thereby being subjected to the restrictions of the Carnot cycle. In order to increase the power of fuel cells, these are often disposed in so-called fuel cell stacks in which a plurality of fuel cells are connected together adjacently or stacked and thus a higher total power can be achieved. Normally, the fuel cell thereby comprises two electrodes which are separated from each other by a membrane or an ion conductor. The anode is subjected to a flow of fuel which is oxidised there. The oxidised positively charged ions migrate through an electrolyte membrane towards the cathode side where they are recombined with the reduced oxidant, such as e.g. air, and are discharged from the fuel cell.
In the construction of modern fuel cell stacks, care must be taken in particular to reduce the size and the weight of the fuel cell stacks so that these can be used in applications where, above all, miniaturisation and weight are to the fore. These are e.g. portable electronic devices or technical-medical devices which are portable on the body or small flying devices.
In U.S. Pat. No. 6,986,961 B1, a fuel cell stack is described, which is constructed from individual fuel cells which follow the standard construction with bipolar plates in which anode and cathode alternate. In this construction, the current flows vertically through the stack so that all the components must be electrically conductive. This is achieved by undulating metal sheets which are embedded in a frame comprising glass fibre-reinforced plastic and are sealed, on the anode side, with a sealing frame. Although the construction with an undulating metal sheet is lighter than production with conventional bipolar plates, a fuel cell stack of this type still has a high weight because of the stainless steel undulating sheets, the high number of components and the high sealing complexity and also the ratio of height to spacing of the undulations which are relatively firmly prescribed by the undulating metal sheet. As a result, the ventilation properties of the separators are restricted.
A further development is represented by the so-called bi-fuel cells. Here, two cells which are electrically insulated from each other are combined such that a fuel cell stack constructed from these cells is constructed in the sequence of cathode, membrane, anode, anode, membrane, cathode or anode, membrane, cathode, cathode, membrane, anode. In US 2005/0 026 021 A1, a stack in the bi-fuel cell type of construction is described, which again loses the saving in weight because of the bi-fuel cell type of construction as a result of solid separator structures and the immission in the fuel. Furthermore, no satisfactory passive ventilation and satisfactory transport away of the reactands is made possible because of the type of construction of the separator structure.